Many watercrafts currently use trim tabs mounted to the transom for attitude control during navigation. Trim tabs, which are also known as “stabilizers”, “trim controls” or “flaps”, are movable plate-like extensions of the hull, usually made of metal, that are hinged to the transom flush with the keel and driven by one or more cylinder actuators to variously tilted positions relative to the keel.
Like in aircraft flaps, appropriate control of watercraft trim tabs provides control of the hydrodynamic force which tends to lift the stern, and consequently lower the bow, thereby ensuring the ideal pitch attitude for navigation in a variety of conditions, for instance according to load distribution, speed, weather and other variables.
Each trim tab is generally driven by a cylinder actuator having ends hinged to the transom and to the trim tab. Such cylinder actuators may be of a hydraulic or electric type and are well known in the art. For instance, U.S. Pat. No. 5,881,666 discloses an electrical cylinder actuator. The actuator disclosed in this document, like all currently available actuators, has slots at its ends for pins designed to secure it to corresponding fixing plates having a coaxial lug integral with the trim tab and with the transom to form hinge connections that allow oscillation of the trim tab according to the length of the piston rod. These connections are obtained by fastening the fixing plates to the corresponding surfaces of the trim tab and/or the transom, by transversely fitting the slots of the cylinder into alignment with the lugs and by axially mounting a pin into the slots/lugs so aligned. Otherwise, the cylinder may be equipped with a hinge already mounted to a fixing plate to be fastened to the corresponding surfaces of the trim tab and the transom. In both cases, the mounting/removal process is particularly laborious and generally requires highly skilled personnel. On the other hand, the cylinder actuator, like any materials designed to operate in contact with seawater, is subjected to wear and often requires maintenance, and hence repeated mounting/removal procedures.